highmem.c

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/*
 * arch/arm/mm/highmem.c -- ARM highmem support
 *
 * Author:  Nicolas Pitre
 * Created: september 8, 2008
 * Copyright:   Marvell Semiconductors Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/highmem.h>
#include <linux/interrupt.h>
#include <asm/fixmap.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include "mm.h"

void *kmap(struct page *page)
{
    might_sleep();
    if (!PageHighMem(page))
        return page_address(page);
    return kmap_high(page);
}
EXPORT_SYMBOL(kmap);

void kunmap(struct page *page)
{
    BUG_ON(in_interrupt());
    if (!PageHighMem(page))
        return;
    kunmap_high(page);
}
EXPORT_SYMBOL(kunmap);

void *kmap_atomic(struct page *page)
{
    unsigned int idx;
    unsigned long vaddr;
    void *kmap;
    int type;

    pagefault_disable();
    if (!PageHighMem(page))
        return page_address(page);

#ifdef CONFIG_DEBUG_HIGHMEM
    /*
     * There is no cache coherency issue when non VIVT, so force the
     * dedicated kmap usage for better debugging purposes in that case.
     */
    if (!cache_is_vivt())
        kmap = NULL;
    else
#endif
        kmap = kmap_high_get(page);
    if (kmap)
        return kmap;

    type = kmap_atomic_idx_push();

    idx = type + KM_TYPE_NR * smp_processor_id();
    vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
#ifdef CONFIG_DEBUG_HIGHMEM
    /*
     * With debugging enabled, kunmap_atomic forces that entry to 0.
     * Make sure it was indeed properly unmapped.
     */
    BUG_ON(!pte_none(get_top_pte(vaddr)));
#endif
    /*
     * When debugging is off, kunmap_atomic leaves the previous mapping
     * in place, so the contained TLB flush ensures the TLB is updated
     * with the new mapping.
     */
    set_top_pte(vaddr, mk_pte(page, kmap_prot));

    return (void *)vaddr;
}
EXPORT_SYMBOL(kmap_atomic);

void __kunmap_atomic(void *kvaddr)
{
    unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
    int idx, type;

    if (kvaddr >= (void *)FIXADDR_START) {
        type = kmap_atomic_idx();
        idx = type + KM_TYPE_NR * smp_processor_id();

        if (cache_is_vivt())
            __cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
#ifdef CONFIG_DEBUG_HIGHMEM
        BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
        set_top_pte(vaddr, __pte(0));
#else
        (void) idx;  /* to kill a warning */
#endif
        kmap_atomic_idx_pop();
    } else if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
        /* this address was obtained through kmap_high_get() */
        kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
    }
    pagefault_enable();
}
EXPORT_SYMBOL(__kunmap_atomic);

void *kmap_atomic_pfn(unsigned long pfn)
{
    unsigned long vaddr;
    int idx, type;

    pagefault_disable();

    type = kmap_atomic_idx_push();
    idx = type + KM_TYPE_NR * smp_processor_id();
    vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
#ifdef CONFIG_DEBUG_HIGHMEM
    BUG_ON(!pte_none(get_top_pte(vaddr)));
#endif
    set_top_pte(vaddr, pfn_pte(pfn, kmap_prot));

    return (void *)vaddr;
}

struct page *kmap_atomic_to_page(const void *ptr)
{
    unsigned long vaddr = (unsigned long)ptr;

    if (vaddr < FIXADDR_START)
        return virt_to_page(ptr);

    return pte_page(get_top_pte(vaddr));
}